NIST conducted its first evaluation of speaker recognition technology in 1996, involving 10 systems completing 4000 trials. In the ensuing nearly 30 years, NIST has conducted approximately 20 Speaker Recognition Evaluations (SREs), with recent SREs typically involving hundreds of systems completing millions of trials. In this talk, we will discuss the history of the NIST SREs, including how the practice of evaluating speaker recognition technology has evolved, current challenges in speaker recognition evaluation, and some possible future directions.